The present invention relates to a composition and method for insulating and protecting structures and, in particular, relates to a composition and method for thermally insulating underground structures and protecting them from corrosion.
In the past, pipes and other structures, particularly underground structures, have been thermally insulated and protected from corrosion by surrounding the structures with various materials such as water repellent granules, various wraps, conduits and the like. Since subterranean structures are frequently subjected to moisture conditions in excess of several feet of hydrostatic head, the problem commonly encountered in the art is to adequately protect these structures from corrosion as a result of moisture intrusion and to provide adequate thermal insulation against heat losses under such conditions.
One prior method of providing thermal insulation and corrosion protection to underground structures was to surround the structure with finely pulverized limestone particles having a water repellent organic coating. Although this material exhibited suitable water repellent properties, due in part to the finely divided nature of the material, it was difficult to handle and to properly compact around the underground structure as a result of its finely divided nature. When the underground structure is being buried, improper compaction of the material around the structure enables foreign objects such as dirt and rocks to penetrate the insulating envelope of material surrounding the structure, thereby destroying the water repellant integrity of the envelope. The presence of the foreign objects in the envelope permits the penetration of moisture into the envelope, resulting in a substantial loss in thermal insulating efficiency as well as the corrosion of the structure.
Expanded perlite and vermiculite have also been used to thermally insulate and protect underground structures. Perlite is a naturally occurring inorganic volcanic rock containing about 2% to about 6% combined water. When the crude rock is crushed and heated to a temperature above about 871.degree. C., the combined water vaporizes and expands the perlite rock to a volume of about 4 to about 20 times greater than its original volume. This expansion process creates a great number of hollow cells in the material which makes the material lightweight and porous and provides it with a low coefficient of thermal conductivity. Vermiculite is another organic material which can also be expanded in a similar manner to a volume from about 6 to about 20 times greater than its original volume to form a similar type of porous, lightweight material having a low coefficient of thermal conductivity. However, when these granular materials are packed around underground structures, they readily absorb soil moisture due to their porous nature. The absorption of soil moisture also results in the loss of thermal insulating efficiency and the corrosion of the underground structure. In some cases, the expanded perlite and the expanded vermiculite materials are coated with water repellant compounds. However, the coated perlite and vermiculite were still ineffective in substantially preventing moisture penetration into the insulating envelope formed around the underground structure.
Thus, a composition which will provide greater resistance to moisture penetration to thereby thermally insulate and protect underground structures from corrosion is still sought.
It is therefore an object of the present invention to provide an improved water retardant composition.
It is a further object of the present invention to provide an improved composition and method for protecting structures from corrosion.
It is another object of the present invention to provide an improved composition and method to thermally insulate structures.